1. Field of the Invention
This invention relates to litter handling systems to facilitate separation of reusable litter particles from solid clumps of animal excrement while keeping the clumps and the litter particles under control so that the removal can be accomplished easily and without unduly exposing to dust from the litter either the person performing the task or the space in which the removal is carried out. The invention also relates to handling solidified clumps of urine-contaminated particles of pet litter material so that they can also be separated from uncontaminated litter particles while keeping both the contaminated and reusable portions of the litter material under control.
2. The Prior Art
A number of structures have been proposed to separate clumps of pet fecal matter from particulate litter so that the fecal matter can be disposed of, while the particulate litter, including, unfortunately, any that has been contaminated by the pet's urine, can be used over again.
U.S. Pat. No. 4,325,325 to Larter describes a three part structure, one part of which is a receptacle containing particulate litter and pet excreta. A second part is an identical, clean receptacle, and a third part is a separator having a flat, apertured screen that fits between the perimeters of both receptacles when one of them is inverted over the other. To separate the animal feces from litter particles that are to be used again, including, in Larter's device, litter contaminated by urine, the perimeters of the three parts of Larter's structure must be held firmly together by hand pressure while inverting the whole assembly to transfer the particulate litter through the screen from the receptacle that originally contained it to the clean receptacle. After it has been inverted, the latter receptacle must be released from the separator while, at the same time, holding the perimeter of the separator firmly in contact with the perimeter of the upper receptacle that still contains feces. This can be very difficult, since the device, laden with litter, can easily weigh 20 lbs., and Larter does not provide clamping means to secure the receptacles to the separator. In addition, the screen apertures are square and the edges of those apertures perpendicular to the direction of movement of the feces and granular material tumbling across the screen during the inversion of the assembly abrade the feces and cause particles of fecal material to pass through the apertures along with the litter that is not supposed to include that contaminant.
U.S. Pat. No. 4,325,822 to Miller shows a structure consisting of a pair of flanged receptacles and a flat separator with rectangular holes. A first set of flanges along the side edges of the separator forms slots into which the side edges of the receptacles must slide. A second set of flanges at the ends of the separator forms latches to connect the assembled parts together so that the assembly can be inverted to pour particulate litter from the first to the second receptacle while retaining solid fecal material in the space between the separator and the first receptacle. The sliding engagement between the side edges of the receptacles and the slots in the separator makes it extremely difficult to use liner sheets in the receptacles due to the pulling and tearing actions on the sheets. In addition, inverting the assembly causes the clumps of fecal material to undergo the same undesirable abrasion on the edges of the rectangular apertures as in the Larter structure.
U.S. Pat. Nos. 3,100,474 to Schneider and 3,908,597 to Taylor disclose a structure into which two receptacles are supported one above the other. At least the upper receptacle has a foraminated bottom through which particulate litter can filter to the lower one. The support structure is arranged to allow a flat plate to be slid between the receptacles as a temporary bottom for the upper receptacle until it is time to change the litter. At that time, the plate is withdrawn to allow particulate material, including material that has been contaminated by urine, to pass through.
U.S. Pat. No. 4,217,857 to Geddie shows three trays stacked together, all facing up. Two of them have solid bottoms, but the third one, which has an apertured bottom, is never mounted between the other two to separate fecal material from particulate litter but is simply nested in the upper tray. Enough litter is then poured into the upper tray to bury the apertured bottom of the third tray. Fecal clumps are separated from the particulate material by lifting the third tray and allowing particulate matter, including any that has been contaminated by urine, to sift through its apertured bottom. One disadvantage of the Miller structure is that the sifting disperses undesired dust in the area. In addition, the trays are not locked together to form an enclosure that can be inverted without any problem when transferring litter from one to the other to be reused.
U.S. Pat. No. 4,299,190 to Rhodes shows a double-deck litter box mounted on pivot bolts to permit it to be turned upside down to dispose of the litter. Rhodes provides no screen between the upper and lower sections, so that inverting the structure transfers all of the litter, both contaminated and not contaminated, to a garbage bag for disposal.
My copending patent application, Ser. No. 618,467, filed Nov. 27, 1990, discloses a litter material particularly suitable as a component in the system of this invention since it contains an adhesive that is activated by liquid in pet excreta, either urine or fecal matter, and, when so activated, joins particles of the litter together into clumps. This makes it possible for the structural components of the system to dispose of both urine and fecal matter with equal ease by separating the clumps, whatever their constituents, from litter material that has not been thus contaminated.